[Search] [txt|pdf|bibtex] [Tracker] [WG] [Email] [Diff1] [Diff2] [Nits]

Versions: 00 01 02 03 04 05 06 07 08 09 10                              
IRTF                                                        E. Lear
Internet Draft                                             R. Droms
Category: Informational                   Name Space Research Group
December 2002
Expires: June 7, 2003


                    draft-irtf-nsrg-report-07.txt
                          What's In A Name:
                        Thoughts from the NSRG

Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as
   Internet-Drafts.

   Internet-Drafts are draft documents valid for a maximum of six
   months and may be updated, replaced, or obsoleted by other
   documents at any time.  It is inappropriate to use Internet- Drafts
   as reference material or to cite them other than as "work in
   progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

Abstract

   Over the last few years, the character of Internet connectivity has
   changed dramatically.  A research group in the IRTF has been
   chartered to review these changes, and make recommendations on
   whether or not remediation within the protocol stack is necessary.
   This document reports the outcome of some of the discussions within
   the research group.

   The key question we will consider is this: does the TCP/IP protocol
   suite need an additional level of naming above layer 3 but below
   the application layer?  In this document, we review the motivation
   for an additional naming mechanism, review related work, propose a
   strawman "stack name" and discuss additional questions, such as the
   structure and use of such names.

   Although this document has a single author, the ideas described are
   those of many people both within and outside of the IRTF (see the
   References and Acknowledgements sections for more details).
   However, others within the NSRG hold views that differ from those
   presented in this document.

Lear, Droms           draft-irtf-nsrg-report-07.txt            [Page 1]


1  Introduction

   The Internet has gone through several metamorphoses, and the use of
   IP addresses in the Internet has changed over time. While routing
   of IP packets has remained largely unchanged, the use and
   assignment of IP addresses has changed considerably.

   For many years, end points, the computers intended to send and
   receive communications, could be named either by IP address or by a
   mnemonic domain name that could be resolved to that address.  The
   static binding between name and address allowed the interchangeable
   use of either to name a host.

   However, several new developments have changed the nature of
   addressing in the Internet:

   * dynamic addressing as provided, for example, through PPP [PPP]
     and DHCP [DHCP]
   * private network address space and network address translators
     (NAT)
   * virtual hosts, where one host is assigned multiple IP addresses
   * load sharing or load balancing, where one IP address is shared by
     multiple hosts, so the services at that address can be provided
     by multiple hosts

   The overall addressing model on the Internet has shifted to one of
   dynamic binding between a host and its address.  A host is assigned
   an address from place to place, or from time to time, when the host
   needs to assert a location in the network topology [BCP5, NAT]. In
   addition, a single IP address can now be shared by multiple servers
   to represent a single logical end point.  The converse is also true
   - a single server can represent multiple logical end points, and
   not even have to use multiple addresses [HTTP11].

   We are not the first to point out the differences between names,
   addresses, and routes.  Shoch delineated those differences as early
   as 1978 in IEN-119 [Shoch].  Saltzer, et al., have also written
   about the nature of naming and addressing [Saltzer92, Saltzer84].
   Research into the nature of names, addresses and routes can help
   provide insight into the current situation, in which the function
   of IP addresses is overloaded to serve the function of a location
   in the network, an interface, a host name, and a portion of that
   which identifies a TCP connection.

   Today we ask the question: given the changing nature of the use of
   IP addresses for end point identification on the network, is
   something more than IP addresses and DNS needed to resolve end
   points?  What functionality would that something bring to the
   table?


Lear, Droms           draft-irtf-nsrg-report-07.txt            [Page 2]


1.1.1  Security Considerations

   In this document we address the notion of identity, which is a key
   component of security, and key to privacy.

   Communications today are secured through one of several means.  For
   strongest protocol security, the communication is encrypted and the
   ends are identified with verifiable public keys.  Several systems
   are available today to do this, including SSH[SSH], the IPSEC
   mechanisms of ESP[ESP] and IKE[IKE], TLS[TLS], and PGP[PGP].

   The absence of a name space that uniquely named a host created
   problems in the design of ESP/AH (so-called "IPsec").  ESP/AH
   really want to bind security associations to a hostname distinct
   from either DNS or IP address, because both the DNS entry and the
   IP address can change when in fact the security association could
   remain valid.  This could occur in the case where a PC moves from
   one point in a topology to another.  In the absence of a persistent
   name in the Internet Architecture, IP addresses are used for the
   binding of Security Associations.  This is an architectural
   shortcoming, not a feature.  Among other advantages, a real unique
   name space would mean that ESP/AH did not care about the
   presence/absence of NAT devices.

   At a different level, there is an expectation that the routing
   system guides a packet toward the destination end point, as
   indicated in the IP destination address.  Until a few years ago,
   this would not have been an unreasonable assumption.  Today
   there are exceptions, particularly transparent web proxies and
   firewalls.

   With some of the currently contemplated changes, the risk of a
   transport connection being hijacked changes.  Instead of having to
   intercept every packet, an attacker may only need to forge a
   rebinding message to one end or the other of a connection.

1.2  How Things Have Changed

   As mentioned earlier, the nature of addressing in the Internet has
   changed.  One important change in the Internet addressing model
   comes from the use of NAT [TRANSP, INAT, NATCOMP].  When a host
   contacts a server to request a web page, it is quite likely that
   the remote address and TCP port, as it appears to the web server,
   will not be the same as the source address and port used by the web
   client.  Furthermore, it is likely to be difficult for the web
   client to determine the address received by server as the client's
   address.  And, a host that has a NAT device between it and the
   Internet cannot become a server because other clients have no way
   to address it.

   Another change to the addressing model in the Internet is that
   computers are far more mobile than they were just a few years ago.

Lear, Droms           draft-irtf-nsrg-report-07.txt            [Page 3]


   When a host moves from one location to another, one's address
   changes to reflect the change in its point of attachment to the
   Internet.  Because TCP bases its transport connection state on IP
   addresses, any connections to the old address are lost (but see
   below).

   One of the largest changes in the character of Internet usage
   involves the resources we access and how we access them.  Whereas
   in the past we intended to access a particular host with a
   particular IP address, today we are likely more interested in
   accessing a service, such as a news service, or a banking service,
   and we are less interested in the host upon which the service sits.
   An industry has built up around the notion these so-called content
   delivery or overlay networks.  The IP address of the web server
   matters only in as much as it will serve the necessary web pages.
   In particular with secure services, what matters most to the user
   is that a particular trusted company has verifiably provided the
   service.

   This brings us to our question: would a new name space enable new
   functionality or return to us old capabilities in the face of NAT,
   DHCP, PPP, and other forms of borrowed IP addresses without unduly
   compromising the Internet architecture in areas such as transport
   protocols and security?

1.3  Why have things changed?

   The most important change the Internet has undergone is spectacular
   growth.  The result of the growth has been shortages in address
   space and routing resources.

   As the growth of the Internet exploded so did address space
   utilization.  A combination of measures, including the introduction
   of private address space, NATs, and a tightening of policy by
   addressing registries reduced the risk of the Internet running out
   of allocatable addresses until the 2010 time frame (or later).  As
   a result, however, the unique identification of an end point and
   the universal ability to reach it was lost.

   At the same time, Internet routing tables exploded in size.  To
   reduce routing tables routes, classless routing [BGP4] was
   developed and deployed to aggregate routes on bit boundaries,
   rather than on old classful boundaries.  Next, the IANA
   discontinued its policy of allocating addresses directly to end
   users and instead allocated them hierarchically to providers,
   requiring providers to show sufficient allocation and utilization
   to justify further assignments.  This retarded for a time the
   explosion in routing, but did not eliminate growth.  While work
   continues in this area, it is important to understand that as of
   this writing the aggregation of routes through CIDR is the most
   efficient way to route Internet traffic, given its current design
   goals.

Lear, Droms           draft-irtf-nsrg-report-07.txt            [Page 4]


   There is a natural conflict between the above two policies.  If one
   allocates addresses in small chunks, more routing entries will
   result.  Periodically providers will renumber to get larger blocks,
   at the inconvenience of all of their customers.

   In summary, the Internet has exploded in size, NATs are now widely
   present, and the use of mechanisms such as PPP and DHCP are widely
   deployed.   In addition, services are now as much or more of
   interest than are individual hosts.  Given all of these changes, is
   it possible to add a new name space that will make connectivity
   more stable and allow us to establish some new operating
   assumptions, such as the ones that these complications broke?

2  Related Work

   There exists a large body of work on name spaces and their
   bindings.  The work we discuss below primarily relates to the
   binding of stacks to IP addresses, with an eye toward mobility or
   transience.

2.1  Mobile-IP

   Mobile-IP addresses the problem of having a stable end point
   identifier on mobile hosts.  As hosts move through the topology
   they update a home agent which acts as an ever-present anchor.
   Mobile-IP provides a different solution depending on whether one is
   using IPv4 or IPv6 [MobileIP, MobileIPv6].  In IPv4, Mobile-IP is a
   tunneling mechanism.  In IPv6, mobile hosts make use of destination
   options.  An end system uses its home address to create transport
   connections and communicate with the other end, one or more
   correspondent nodes.  IPV4 mobile hosts are tunneled through a home
   agent and optionally a foreign agent, so that the end system's
   address space is found in the routing system without additional
   global routing overhead.  In IPv4 the home agent is separate from
   the other end of a transport connection, and packets take a
   triangular route.  In IPv6, support of mobility is required, and
   the likely non-mobile host, the correspondent node, is aware that
   the other end is mobile.  Therefore, once the mobile host and
   remote host establish communications they can "short circuit" to
   remove the home agent.  This is key because while the foreign agent
   is likely to be near the mobile host, the home agent is unlikely to
   be near anybody.

Lear, Droms           draft-irtf-nsrg-report-07.txt            [Page 5]


     _______                      ________
    |       |Care-of Address     |        | foreign agent optionally
    |Mobile |--------------------| Remote | forwards packets to mobile
    | Host  |                    | Agent  | host
    |_______|                    |________|
       ::Home Address                |
       ::                            |  home agent encapsulates and passes
       ::                            |  packets to the remote agent or
       ::                         ___|____  directly to the mobile node
       ::                        |        |
       ::                        | Home   |
       ::                        | Agent  |\  remote host sends packets
       ::                        |________| \ to home agent
       ::                                    \
       \\                                     \
        \\                                     \
         \\                                     \_____________
          \\  tunneled transport connection     |             |
           =====================================|Correspondent|
                                                |    Node     |
                                                |_____________|

          Figure 1: Mobile-IPv4

   In effect, Mobile-IP turns the mobile node's IP address into a host
   identifier, where the "care of" address is the host's current
   location.  The way Mobile-IP succeeds is that it uses tunneling
   within the topology to represent an address at one location when it
   is in fact at another.  However, a route to the mobile node's
   address itself must be available within the topology at all times.
   In an IPv4 world this would be untenable because of constraints on
   both the addressing system.  With IPv6, the addressing pressures
   are off, and so each host can have a unique end address.  However,
   problems remain with the routing system.  In addition, there is a
   class of devices for which there may be no "home", such as devices
   in airplanes, mobile homes, or constant travelers.  Additionally,
   there is a desire within some of the mobility community to have
   "micromobility" mechanisms that enable faster movement than
   envisioned by Mobile-IP.  The Routing Research Group (rrg) is
   currently investigating this area.

   Most importantly, mobile devices can't withstand the loss of the
   home agent, even if they are still online somewhere. With the home
   agent offline, no incoming connections can get to them, and
   long-lived communications cannot be re-established. If the
   rendezvous point location/identity wasn't overloaded on the home
   address (which is, of necessity, a place in the network, and might
   go offline, not a distributed database), it might be possible to
   work around that for those entities that cared about that failure
   mode.

Lear, Droms           draft-irtf-nsrg-report-07.txt            [Page 6]


   2.2  Stream Control Transport Protocol (SCTP)

   Many of the problems raised have to do with the use of layer 3
   information at higher layers, such as the use of a layer 3 address
   as the end point identifier for a TCP connection and the use of
   layer 3 addresses in the pseudo-header in TCP.  SCTP, an
   alternative to TCP, uses IP addresses in a more dynamic way as the
   identifiers for connection endpoints. TCP transport connection end
   points are named by IP addresses, and there are precisely two end
   point addresses, one for each end.  SCTP allows for multiple
   transport addresses per end, nominally for redundancy of
   applications that require high availability.  However, it is
   possible to move a transport connection as a host moves from one
   location to another, or as its address changes due to renumbering
   (for whatever purpose).  Work has progressed within the IETF to
   introduce a new capability to SCTP, that allows connection end
   points to change the set of IP addresses used for a transport
   connection.[ADDIP]

   There are three limitations to this idea.  For one, it only affects
   those hosts that use SCTP, and so long as there exist other
   transports that are considered more appropriate for specific tasks,
   solving an Internet naming problem within SCTP will be susceptible
   to the charge that the solution is not sufficiently general.

   The second problem is that as contemplated in the draft the risk of
   an attacker hijacking a connection is elevated.  This same
   problem exists within MobileIP, and may similarly be mitigated by
   purpose built keys (see below).

   Finally, because SCTP does not have a home agent, SCTP does not
   handle what some would argue is a corner case, when two nodes
   change their location at the same time.

2.3  Host Identity Payload

   Host Identity Payload (HIP) is a new approach to the problem of
   naming end points.  It inserts an additional "name" between layer 3
   and layer 4, thus becoming layer 3.5.[HIP-ARCH] The goal is to
   decouple the transport layer from the Internet layer, so that
   changes in the Internet layer do not impact the transport, and the
   benefit is shared by all mechanisms atop transports that use HIP.

Lear, Droms           draft-irtf-nsrg-report-07.txt            [Page 7]


             ______________________________________
            |                                      |
            |            Application               |
            |______________________________________|
            |                                      |
            |             Transport                |
            |______________________________________|  The Host Stack
            |                                      |
            |         HIP or ESP w/ HI as SPI      |
            |______________________________________|
            |                                      |
            |             IP Header                |
            |______________________________________|


                   Figure 2: Host Identity

   HIP itself relies on a cryptographic host identity (HI) that is
   represented in a Host Identity Tag (HIT) of various forms.  One is
   a hash of the public key host identity, another is an
   administratively assigned value coupled with a smaller hash of the
   public key host identity.  Host identities can be public or
   anonymous, the difference being whether or not they are published
   in a directory.

   Whereas today one binds the transport to an IP address, HIP
   proposes that the transport binds to a host identity tag (HIT).
   DNS is used to determine the HI and HIT, or to validate via reverse
   lookup an HIT.  Further, DNS continues to be used to get an
   Internet address.

   Whether one should want to decouple the transport layer from the
   Internet layer is a controversial question.  After all, that
   coupling has for many years provided the barest bones of the
   security of knowing that the packets that make up the transport
   connection are being guided through the network by routing
   tables in Internet routers that are owned by people and
   organizations whose intent is to get one's packets from source to
   destination.  If we divorce the transport from the Internet layer,
   we introduce another way for an attacker to potentially hijack
   connections.  HIP attempts to address this through the use of
   public key verification.

   Additionally, HIP raises an issue regarding other uses for
   aggregation of IP addresses.  Today, they are not only aggregated
   for purposes of reduced routing, but also for reduced
   administration.  A typical access list used on the Internet will
   have some sort of a mask, indicating that a group of hosts from the
   same subnet may access some resource.  Because the value of a HIT
   is a hash in part, only the administratively assigned value can be
   aggregated, introducing an allocation limitation and authorization
   concerns.

Lear, Droms           draft-irtf-nsrg-report-07.txt            [Page 8]


   On the other hand, there is the old computer science saying, any
   problem can be fixed by an additional layer of indirection
   (arguably what we're talking about).  It should be possible to
   administratively aggregate on groupings that are made at higher
   layers.

   An alternative approach would be to aggregate based on DNS names,
   rather than HI values.  See [HIP-ARCH] for more details.

   A key concern with HIP is whether or not it will work in a mobile
   world.  If the DNS is involved, or if any directory is involved,
   will caching semantics eventually limit scalability, or are there
   mobility mechanisms that can be employed make use of directories
   feasible?

2.4  Purpose Built Keys

   Purpose built keys (PBKs) are temporary end point identifiers that
   are used to validate a given endpoint during a communication.  PBKs
   are similar to HIP [PBK]. Rather than attempting to build an
   infrastructure to validate the end points, however, PBK's sole
   purpose is to ensure that two hosts that originate a communication
   may continue that communication with the knowledge that when
   finished each end point will be the same end point it was at the
   start.  Thus, even if one's address changes for whatever reason it
   is still possible to validate oneself to the other side of the
   communication.

   PBKs make no claim as to who the parties actually are.  They make
   no use of public key infrastructures.  PBKs are themselves
   ephemeral for the duration of a communication.

   PBKs take the form of ad hoc public/private key pairs.  When a
   node wishes to validate itself to another node it signs a piece of
   data with its private key that is validated by the other end with
   the public key.  The public key itself becomes an end point
   identifier.

   PBKs might be instantiated in several different places in the
   stack; for example, carried in an IPv6 header extension or used by
   an application protocol.

2.5  RSIP and MIDCOM

   Two related efforts have been made to stitch together name spaces
   that conflict.  One is RSIP, which allows for the temporary
   allocation of address space in one "realm" by a host in another
   realm, not unlike the way an address is gotten via DHCP.  The
   benefit of RSIP is that it allows the end point to know what
   address it is assigned, so that it may pass such information along
   in the data path, if necessary.  The problem with RSIP is that host
   routing decisions within the stack are very complex.  The host

Lear, Droms           draft-irtf-nsrg-report-07.txt            [Page 9]


   makes decisions based on destination address (a process that a fair
   amount of configuration, and lacked certainty as it was based on
   potentially non-unique IP addresses).  Because RSIP borrows public
   addresses it must relinquish them as quickly as possible, or the
   point of NAT is negated.  In order to make better use of the scarce
   public resource, RSIP implementations would need to route not just
   on destination address, but on application information as well.
   For example, internal hosts would probably not need external
   addresses merely to browse the web.

   MIDCOM is a similar approach.  However, rather than tunneling
   traffic, an agreement between an end point and its agent and a
   "middle box" such as a NAT or a firewall is made so that the end
   point understands what transformation will be made by the middle
   box.  Where a NAT or a web cache translates from one name
   space to another, MIDCOM enables end points to identify that
   translation.

   MIDCOM is contemplated for use by specific applications, and thus
   avoids the stack problems associated with RSIP.  However, neither
   MIDCOM nor RSIP resolve how to discover such middle boxes.  Nor do
   they provide a unique way for a host behind a NAT to identify
   itself in an enduring way.  Finally, they both run into problems
   when multiple NATs are introduced in a path.

2.6  GSE or "8+8"

   One proposal attempts to ease the conflict between the desire of
   end systems to have a fixed name for themselves, and the needs of
   the routing systems for address assignments which minimize the
   overhead of routing calculations. The clash between these two
   desires produces either the inconvenience (for the end systems) of
   renumbering, or routing inefficiency and potentially poor address
   space utilization as well; the latter caused by the difficulty of
   renumbering to allows effective use of address space.

   Known as 8+8 or GSE, it would have split the IPv6 address into two
   parts: a routing system portion that would be assigned and managed
   by service providers that would change based on routing system
   requirements, and a locally managed portion that would be assigned
   and managed by terminal autonomous systems [GSE]. While each portion
   is globally unique, there are in effect two addresses, one to get a
   packet to an autonomous system and another to get to the host.
   Further, end hosts might not be aware, at least initially, of their
   routing portions.  It was envisioned that the renumbering of
   the routing portion could be done as a matter of signaling, with
   little administrative involvement from the end point.  Another goal
   of GSE was to eliminate additional routing overhead caused by
   multihomed end systems, whose information must today be carried
   throughout the routing system.  By allowing end enterprises to have
   multiple global parts for purposes of multihoming, the terminal
   ASes would become what are today's last-hop ISPs.  There are a

Lear, Droms           draft-irtf-nsrg-report-07.txt            [Page 10]


   number of challenges that GSE would have to overcome.  For one, how
   does one glue together the provider portion of an address with the
   more local part, and how would one accomplish the task securely?
   Would doing so eliminate the need or interest in adding other
   additional name spaces?

2.7  Universal Resource Names

   Universal resource names (URNs) do not provide us a mechanism to
   resolve our naming concerns [URN]. Rather, they may provide us the
   form of the name to use, and perhaps a framework for resolution.
   For instance, an HI may conceivably be represented as a URN.  URNs
   further the notion of defining a binding and boundaries between the
   name of an object and its location.

3.  Discussion: Users, Hosts, Entities and Stacks

   The original addressing architecture of IP and TCP assumed that
   there is a one-to-one relationship between an IP address and a
   communicating "entity."  By "entity," we mean an identifiable
   participant in an Internet communication.  Examples of an entity
   include a host, a user, a client program or a service.  This
   one-to-one relationship between IP address and entity was assumed
   to exist throughout the duration of a "session" (usually a TCP
   connection); that is, all of the IP datagrams exchanged during a
   session would share the same endpoint identifiers, and the endpoint
   identifiers in those datagrams would not be altered as the
   datagrams traversed the Internet.

   There is also an assumption that the binding between an entity and
   an IP address would vary only infrequently over time.  DNS allows
   for the binding between a domain name for a host and its IP address
   to vary over time, but changes in those bindings may propagate
   slowly and do not accommodate frequent changes.

   As explained in section 1, the underlying addressing architecture
   of the Internet has changed, leading to the need for new naming
   mechanisms that function with host mobility, the instantiation of
   multiple entities on a single host and the instantiation of a
   single entity across multiple hosts, and that can provide security
   independent of IP addressing.

   When a host moves from one location to another, or when a
   host receives a new address for some other reason, the computer
   itself has largely remained the same, as has the person using it.
   The identity of that computer has not changed.  That entity may
   well be in communication with other computers and have access
   rights to network resources.  Indeed, multiple entities may be
   represented by a single computer.

   Today, a host may represent multiple entities.  This happens when a
   service provider hosts many web sites on one server.  Similarly, a

Lear, Droms           draft-irtf-nsrg-report-07.txt            [Page 11]


   single entity may be represented by multiple hosts.  Replicated web
   servers are just such an example.  We refer to these entities as
   "stacks", instantiations of the TCP/IP model, be they across one or
   many hosts.  We define a stack as one participant or the process on
   one side of an end-to-end communication.  That participant may move
   and may be represented by multiple hosts.

   Each instance of a stack has a name, a "stack name".  At an
   architectural level the Name Space Research Group debated the value
   of such names, and their associated costs.  We see forms of this
   name used in numerous places today.  As previously mentioned, SSH
   uses public/private key pairs to identify end points.  An HTTP
   cookie anonymously identifies one end of a communication, in such a
   manner that both the transport connection and the IP address of the
   other end point may change many times. Stack names are intended to
   identify mobile nodes, devices behind NATs, and participants of a
   content delivery or overlay network.

   When two devices represent a single end point they must share state
   in order to keep the other end from becoming confused (to say the
   very least).  When doing so, such stacks may indeed consist of
   multiple processes on each end.  One view is that such processes
   can theoretically be named independently of the Internet layer,
   allowing for sessions to migrate at the behest of applications.
   However, it is not possible to standardize migration independent of
   applications, who retain state in all manner of places, from
   configuration files to memory.  Additional names of such processes
   serve only to identify those who are authorized somehow to
   represent the end point, and do not themselves alleviate effort
   required to ensure application consistency.

   We use the word "sessions" above, a mechanism that the current IP
   stack does not formally provide.  If we were to have a session
   layer in the classic sense it might sit above the transport layer,
   and a session could consist of more than a single transport
   connection.  If we view the session at below the transport layer,
   then transport connections can be bound to an identifier of some
   form other than that of the IP address, and transport connections
   could persist across IP address changes.  It is unlikely, however,
   that anything that the transport layer binds to would entirely
   obviate the need for sessions above the transport layer.


3.1 Requirements, desirable features and design decisions

   Stack names are defined to be a new naming structure integrated
   into Internet addressing, which provide a solution to several
   problems in the current addressing architecture.  We have
   identified several requirements for this naming structure.  Stack
   names will allow continuation of sessions independent of host
   mobility or other host renumbering.  A stack that spans several
   host is identified by a single stack name, and multiple stacks on a

Lear, Droms           draft-irtf-nsrg-report-07.txt            [Page 12]


   single host are unambiguously identified by separate stack names.
   Stack names allow authentication of stack identity, authentication
   of the origin and contents of messages and privacy for message
   contents.  Finally, the stack name architecture will interoperate
   with existing Internet infrastructure, including existing host
   implementations and core routing, for backward compatibility.

   Stack names are intended to address as many of the problems in the
   current Internet addressesing as possible, including: NAT,
   mobility, renumbering, multiple entities on one host and entities
   that span multiple hosts.  Stack names should be globally unique,
   so that state about stack names, such as mapping information, need
   not be kept in the network.  Stack names should also provide
   anonymity, so that users or other entities cannot be easily
   identified through a stack name.

   These requirements and features lead to several design decisions:
   * Internal structure: opaque/structured,
     fixed-length/variable-length, universally-unique/random-unique
   * Position in stack
   * Mapping to mnemonic name (are stack names ever visible to
     humans?)
   * Relationship between stack names and routing system

3.2.  What do stack names look like?

   Names may be structured or unstructured.  If they are structured,
   what encoding do they use, and what is their scope?  Is the length
   of such a name fixed or variable?  Are stack names unique across
   the Internet?  If so, are they guaranteed unique through some sort
   of a registry or are they statistically unique?  If it is a
   registry, is it centralized or distributed, such as DNS?  The
   remainder of this section summarizes the discussion within the NSRG
   on these questions.

   As we have seen, one possibility is that stack names could be
   represented as MOBILE-IP home addresses.  The benefit of this idea
   is that one might well derive a large benefit without having to
   incur any additional protocol engineering, at least initially.  By
   representing stack names in this way the architectural distinction
   between stack name and location is somewhat muddled.  If the goal
   is to separate location and entities, where an IP address
   represents location, a Mobile-Ipv6 answer doesn't get us to the
   goal.


3.2.1 Uniqueness

   This document would not exist were uniqueness not desirable, since
   we could live on with the current state of affairs (and we may
   yet).  Uniqueness offers certainty that a name represents exactly
   one object.  DNS A records never were intended to have uniqueness.

Lear, Droms           draft-irtf-nsrg-report-07.txt            [Page 13]


   and as we've discussed, IP addresses, particularly in a V4
   environment, no longer have uniqueness.  Uniqueness allows for
   people and programs to build operating assumptions the other end of
   a communication.  TCP was designed with such an assumption.

   Being uniquely identified also raises security concerns.  What if
   you don't want to be uniquely identified by generators of SPAM or
   by powerful entities such as governments?  Note that we refer to
   the uniqueness of the object referenced by the identifier.  An
   object itself might have multiple names.

3.2.4  Statistical Uniqueness versus Universal Uniqueness

   The classic way we have ensured uniqueness of names and addresses
   on the Internet has been to have those names and addresses assigned
   by central authorities through a distributed tree-structured
   database.  The overhead for name assignment may be distributed
   through delegation of authority. While this mechanism for name
   assignment guarantees uniqueness to the level of competence of
   those authorities, such delegation introduces overhead, artificial
   markets, trademark concerns, and other problems.

   Some members of the NSRG are concerned that any new registry for
   stack names would bring unwelcome and burdensome administrative
   costs to connecting to the Internet, either as a service or a user.
   One could envision a very large reverse lookup domain that contains
   all HIs, leaving little room for decentralization.

   In particular we have seen two problems [el1]crop up with centralized
   name spaces.  The first problem is that of domain squatting, where
   people buy a name simply for its usefulness to others.  The second
   problem lies with IP addresses, which are allocated and sold by
   providers.  Those providers may choose to make a "service" out of
   making addresses available to customers.  When designing a new name
   space, one should introduce no artificial scarcity.

   One way to avoid a new administrative overhead would be for
   individuals to be able to generate statistically unique names.
   Statistically unique names can easily be mapped TO, but they are
   less easily mapped FROM.  This is because it is difficult to
   establish trust relationships necessary to make changes to the
   mapping.  For instance, if a central authority controls the name
   space, there must be some sort of authentication and authorization
   model in place for the change to be allowed.  If such a mechanism
   is in place, one has to wonder (a) why the names used for that
   infrastructure are not used and therefore (b) why statistically
   unique names would be of any advantage.

   There was a consensus that if we were to introduce a new name space
   it should not be mnemonic in nature.  DNS exists for that purpose
   today, and while others have recently identified a need to revisit
   DNS, that was not the purpose of this effort.

Lear, Droms           draft-irtf-nsrg-report-07.txt            [Page 14]


3.2.2 Mapping

   This brings into question several related concerns with naming:
   what, if any, mapping mechanisms exist?  Should stack names map to
   IP addresses, to domain names, or for that matter, to anything?
   Do domain names, X.509 distinguished names, or other names map to
   stack names?  Each is a separate question.  A name on its own is of
   very limited value.  The mappings go to how the name will be used.
   Is a stack name just something that sits in a transport control
   block on a device?  In effect purpose built keys could accomplish
   that task.

3.2.3  Anonymity

   Related to uniqueness and mapping is anonymity.  Is it possible or
   even desirable to have anonymous names?  That is, should my
   computer be able to establish a communication to your computer,
   such that you can be assured that you are communicating with the
   same entity who used a particular name, without actually knowing
   the underlying binding between the name and the object?

3.2.5 Fixed versus variable length names

   When the nature of the name is decided one must decide whether the
   name should be of fixed length or whether it is variable length.
   Traditionally those fields which are found in every packet tend to
   be fixed length for performance reasons, as other fields beyond
   them are easily indexed.  The form the name takes will have some
   relevance on this decision.  If the name appears along the lines of
   an X.509 distinguished name, it must be variable.  If the name is
   otherwise fixed length and supposed to be universally unique, the
   field must allow for large enough numbers to not require a protocol
   change anytime soon.  Similarly, if the name is statistically
   unique, the field must be large enough so that the odds of a
   collision are acceptably low so that the protocol needn't change
   anytime soon.  We leave it to engineers to determine what "anytime
   soon" and "acceptably low" are.

   A convenient feature of a variable-length name is that it allows
   for ease of organizational delegation.  If one provides a
   hierarchical model such as DNS, one can decentralize authority to
   get a new name or to change a name.  By the same token, such
   structure requires a root authority from which distribution
   occurs.  So long as the name itself is not a pneumonic, perhaps it
   is possible to limit problems such as domain squatting.

   Ultimately, if the name is to be other than statistically unique,
   there will be some sort of central root service.

3.3  At what layer are stack names represented?

   Where are stack names represented?  Are they represented in every

Lear, Droms           draft-irtf-nsrg-report-07.txt            [Page 15]


   packet, or are they represented in only those packets that the
   underlying use requires?  The benefit of not requiring stack names
   to appear in every packet is some amount of efficiency.  However,
   the benefit of having them in every packet is that they can be used
   by upper layers such as ESP.  In addition, end points would be able
   to distinguish flows of packets coming from the same host even if
   the IP address changes, or if the remote stack migrates to another
   piece of hardware.  The PBK approach would alert an end point when
   one side knows of such a change, but as we have seen, the IP
   address one side sees, the other side may not, without a mechanism
   such as MIDCOM or RSIP.  HIP and ESP solve this problem by putting
   an identifier (either the HIT or SPI) in every packet.

           ______________________________
          |   ______          ______     |
          |  /_____ /|       /_____ /|   |
          | | APP  |f|      | APP  |b|   |
          | |------|o|      |------|a|   |
          | |TRANS |o|      |TRANS |r|   |
          | | PORT |.|      | PORT |.|   |
          | |------|c|      |------|c|   |
          | | IP   |o|      | IP   |o|   |
          | |______ m|      |______ m|   |
          | | MAC  |/       | MAC  |/    |
          | |______/        |______/     |
          |                              |
          |                              |
          |______________________________|

       Figure 3: One application: multiple stacks on a single device

   If we had a stable Internet layer it might be possible to
   represent stack names as IP addresses.  Even if a host moved, a
   stack name could be represented as a Mobile-IP "home" address.  The
   PBK proposal suggests that stack names be passed as necessary as
   end to end options in IPv6 or simply as options in IPv4.

Lear, Droms           draft-irtf-nsrg-report-07.txt            [Page 16]


            __________________   ________________________
           |                  | |                        |
           |   _______________| |____________________    |
           |  /_______________| |___________________ /|  |
           | |       A P P L I| |C A T I O N        |f|  |
           | |----------------| |-------------------|o|  |
           | |        T R A N | | P O R T           |o|  |
           | |----------------| |-------------------|.|  |
           | |         I N T E| |R N E T            |c|  |
           | |----------------| |-------------------|o|  |
           | |         F R A M| | I N G             |m|  |
           | |----------------| |-------------------| /  |
           | |________________| |___________________|/   |
           |                  | |                        |
           |__________________| |________________________|

   Figure 4: Another application: single stack represented by
             multiple hosts

   If we do not assume a stable Internet layer, then stack names must
   appear above it.  If we insert a new mechanism between the Internet
   and transport layers, all end points that wish to use the mechanism
   would need to change.

3.3.1 A few words about transport mechanisms

   We may not wish to completely divorce the transport layer from the
   Internet layer, as currently implemented.  The transport mechanisms
   today are largely responsible for congestion control.  If one end
   point moves it is quite possible that the congestion
   characteristics of the links involve will change as well, and it
   thus might be desirable for mechanisms such as TCP Slow Start to be
   invoked.  It is also possible that codecs may no longer be
   appropriate for the new path, based on its new characteristics.  In
   as much as mobile hosts change their locations and bindings with
   MOBILE-IP today, this is already an issue.

3.4  Stack names and the routing system

   It would seem a certainty that the routing system would want very
   little to do with stack names.  However, as previously mentioned,
   when we break the binding between Internet and transport layers, we
   now must take some care to not introduce new security problems,
   such that a transport connection cannot be hijacked by another host
   that pretends to be authorized on behalf of an end point.

   One misguided way to do this would be to enforce that binding in
   the routing system by monitoring binding changes. In order for the
   routing system to monitor the binding, it realistically must be
   done out in the open (i.e., not an encrypted exchange) and the
   binding must appear at some standard point, such as an option or at

Lear, Droms           draft-irtf-nsrg-report-07.txt            [Page 17]


   a predictable point in the packet (e.g., something akin to layer
   3.5).

   In other words, one would have gone all the way around from
   attempting to break the binding between transport and Internet
   layers to re-establishing the binding through the use of some sort
   of authorization mechanism to bind stack names and Internet
   addresses.

3.5  Is an architectural change needed?

   The question of what level in the stack to solve the problem
   eventually raises whether or not we contemplate architectural
   changes or engineering enhancements.  There can be little dispute
   that the topic is architectural in nature.  For one, there are now
   numerous attempts to solve end point identification problems within
   the engineering space.  We've already mentioned but a few.  The
   real question is whether the existing architecture can cover the
   space.  Here there are two lines of thought.  The first is that the
   use of mobility mechanisms and MOBILE-IP will cover any perceived
   need to provide stack names.  Assuming that it can be widely and
   securely deployed, MOBILE-IP certainly resolves many host mobility
   concerns.  However, it remains to be seen if it can address other
   problems, such as those introduced by content delivery networks.

   The other line of thought is that we should make the architectural
   distinction between names, addresses, and routes more explicit
   since there is otherwise an overloading of operators.  Regardless
   of whatever tactical benefit one might gain, the sheer
   architectural separation should provide value in and of itself over
   time.  The risk of this argument is that we will have introduced
   complexity without having actually solved any specific problem,
   initially.

   To resolve the differences between the two schools of thought
   requires development of the latter idea to the point where it can
   be properly defended, or for that matter, attacked.

4  Conclusions or Questions

   The NSRG was not able to come to unanimity as to whether an
   architectural change is needed.  In order to answer that question,
   as just noted in the previous section, the notion of a stack name
   should be further developed.

   Specific questions that should be answered are the following:

   1.  How would a stack name improve the overall functionality of the
       Internet?
   2.  What does a stack name look like?
   3.  What is its lifetime?
   4.  Where does it live in the stack?

Lear, Droms           draft-irtf-nsrg-report-07.txt            [Page 18]


   5.  How is it used on the end points?
   6.  What administrative infrastructure is needed to support it?
   7.  If we add an additional layer would it make the address list in
       SCTP unnecessary?
   8.  What additional security benefits would a new naming scheme
       offer?
   9.  What would the resolution mechanisms be, or what
       characteristics of a resolution mechanisms would be required?

   Of the many existing efforts in this area, what efforts could such
   a name help?  For instance, would a stack name provide for a more
   natural MIDCOM design?

   This document raises more questions than answers.  Further studies
   will hopefully propose valid answers.

5  Further Studies

   Various efforts continue independently.  One outgrowth is the
   possibility of a HIP working group within the IETF.  Although this
   work might occur within the IETF, it should be noted that there is
   a risk to attempting to standardize something about which we yet
   have the full benefit of having explored in research.

   Work on relieving stress between routing and addressing also
   continues within the IETF in the MULTI6 and PTOMAIN working groups.

   A separate effort proceeds elsewhere in the research community to
   address what the Internet should look like ten years from now.
   There-in we suspect that stack names will play a considerably
   larger role.

   It is possible that work will continue within the IRTF.  However,
   that work should be conducted by smaller teams until mature
   proposals can be debated.  Questions of "whether additional name
   spaces should be introduced" can only be answered in such a manner.

6  Acknowledgments

   This document is a description of a review done by the Name Space
   Research Group of the Internet Research Task Force.  The members of
   that group include: J. Noel Chiappa, Scott Bradner, Henning
   Schulzrinne, Brian Carpenter, Rob Austien, Karen Sollins, John
   Wroclawski, Steve Bellovin, Steve Crocker, Keith Moore, Steve
   Deering, Matt Holdrege, Randy Stewart, Leslie Daigle, John
   Ioannidis, John Day, Thomas Narten, Bob Moskowitz, Ran Atkinson,
   Gabriel Montenegro, and Lixia Xiang.

   Particular thanks go to Noel Chiappa whose notions and continuing
   efforts on end points kicked off the stack name discussion.  The
   definition of an endpoint is largely taken from Noel's unpublished
   draft.  Thanks also to Ran Atkinson and Bob Moskowitz whose

Lear, Droms           draft-irtf-nsrg-report-07.txt            [Page 19]


   comments can be found (in some cases verbatim) in this document.

   The idea of GSE or 8+8 was originally developed by Mike O'Dell.
   The documents in which GSE is described are not published as RFCs.

7. Author's Address

   Eliot Lear
   Cisco Systems, Inc.
   170 West Tasman Dr.
   San Jose, CA 95134
   Phone: +1 408 527 4020
   EMail: lear@cisco.com

8.  References

   [DHCP] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131,
   March, 1997.

   [BCP5] Rekhter, Y. et al, "Address Allocation for Private
   Internets", BCP-5 (RFC 1918), February, 1996.

   [NAT]  Srisuresh, P., Holdrege, M., "IP Network Address Translator
   (NAT) Terminology and Considerations", RFC 2663, August 1999.

   [Shoch] Shoch, J., "Inter-Network Naming, Addressing and Routing",
   Proceedings of IEEE Compcon, pp 72-97, Fall, 1978.

   [GSE] O'Dell, M., "GSE - an alternate addressing architecture for
   IPv6", draft-ietf-ipngwg-gseaddr-00.txt, 1997.

   [Saltzer92] Saltzer, J.,  "On The Naming and Binding of Network
   Destinations", RFC 1498, September, 1992 (as republished).

   [Saltzer84] Saltzer, J, Reed, D., Clark, D., "End-To-End Arguments
   in System Design", ACM Transactions on Computer Systems, Vol. 2,
   No. 4, November, 1984.

   [TCP]  Postel, J., "Transmission Control Protocol", RFC 792,
   September, 1981.

   [MCAST] Deering, S.E., "Host Extensions for IP multicasting",
   RFC 1112, August, 1989.

   [SSH] Ylonen, T., et. al, "SSH Protocol Architecture", Work in
   Progress, draft-ietf-secsh-architecture-12.txt, January, 2001.

   [ESP] Kent, S., Atkinson, R., "IP Encapsulating Security Payload
   (ESP)", RFC 2406, November, 1998.

   [IKE] Harkins, D., Carrel, D., "Internet Key Exchange", RFC 2409,
   November 1998.

Lear, Droms           draft-irtf-nsrg-report-07.txt            [Page 20]


   [TLS] Dierks, T., Allen, C., "The TLS Protocol Version 1.0",
   RFC 2246, January, 1999.

   [TRANSP] Carpenter, B., "Internet Transparency", RFC 2775,
   February, 2000.

   [INAT] Hain, T., "Architectural Implications of NAT", RFC 2993,
   November, 2000.

   [NATCOMP] Holdrege, M., Srisuresh, P., "Protocol Complications
   with the IP Network Address Translator", RFC 3027, January, 2001.

   [BGP4] Rekhter, Y., Li, T., "Border Gateway Protocol 4 (BGP-4)",
   RFC 1771, March, 1995.

   [MobileIP] Perkins, C., "IP Mobility Support", RFC 2002,
   October, 1996.

   [MobileIPv6] Johnson, P., Perkins, C., "Mobility Support in IPv6",
   Work in Progress, draft-ietf-mobileip-ipv6-18.txt, June, 2002.

   [ADDIP] Stewart, et. al., "SCTP Extensions for Dynamic
   Reconfiguration of IP Addresses", Work in Progress,
   draft-ietf-tsvwg-addip-sctp-05.txt, May, 2002.

   [HIP-ARCH] Moskowitz, B., "Host Identity Payload Architecture",
   Work in Progress, draft-moskowitz-hip-arch-02.txt, February, 2001.

   [PBK] Bradner, S., Mankin, A., Schiller, J., "A framework for
   Purpose Build Keys (PBK)", Work in Progress,
   draft-bradner-pbk-frame-01.txt, July, 2002.

   [URN] Sollins, K., "Architectural Principles of Universal Resource
   Name Resolution", RFC 2276, January, 1998.

   [ESMTP] Klensin, J. (Ed), "Simple Mail Transfer Protocol",
   RFC 2821, April, 2001.

9.  Intellectual Property Statement

   The IETF takes no position regarding the validity or scope of any
   intellectual property or other rights that might be claimed to
   pertain to the implementation or use of the technology described in
   this document or the extent to which any license under such rights
   might or might not be available; neither does it represent that it
   has made any effort to identify any such rights.  Information on
   the IETF's procedures with respect to rights in standards-track and
   standards-related documentation can be found in BCP-11.  Copies of
   claims of rights made available for publication and any assurances
   of licenses to be made available, or the result of an attempt made
   to obtain a general license or permission for the use of such
   proprietary rights by implementors or users of this specification

Lear, Droms           draft-irtf-nsrg-report-07.txt            [Page 21]


   can be obtained from the IETF Secretariat.

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
   rights which may cover technology that may be required to practice
   this standard.  Please address the information to the IETF
   Executive Director.

10.  Full Copyright Statement

   Copyright (C) The Internet Society (2002).  All Rights Reserved.

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain
   it or assist in its implementation may be prepared, copied,
   published and distributed, in whole or in part, without restriction
   of any kind, provided that the above copyright notice and this
   paragraph are included on all such copies and derivative works.
   However, this document itself may not be modified in any way, such
   as by removing the copyright notice or references to the Internet
   Society or other Internet organizations, except as needed for the
   purpose of developing Internet standards in which case the
   procedures for copyrights defined in the Internet Standards process
   must be followed, or as required to translate it into languages
   other than English.  The limited permissions granted above are
   perpetual and will not be revoked by the Internet Society or its
   successors or assigns.  This document and the information contained
   herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND
   THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES,
   EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT
   THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR
   ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A
   PARTICULAR PURPOSE."

11.  Expiration Date

   This memo is filed as <draft-irtf-nsrg-report-07.txt>, and expires
   June 7, 2003.















Lear, Droms           draft-irtf-nsrg-report-07.txt            [Page 22]